The present invention, in some embodiments thereof, relates to a plunger seal for a medicine cartridge (e.g. a syringe) and, more particularly, but not exclusively, to a plunger seal with adjustable sealing force against an inner wall of the syringe.
U.S. Pat. No. 5,411,489 discloses “pre-filled syringes equipped with an improved plunger, a plunger actuating cylinder and a plunger rod, characterized by a leak-proof seal and easy sliding property”.
U.S. Pat. No. 6,090,081 discloses “a sealing stopper for a syringe, having very high sealing property and sliding property, and a prefilled syringe using this sealing stopper and capable of preserving a medicament for a long time and operating in easy and precise manner during injecting. This syringe is also excellent in sanitary and operating property during a step of formulation or preservation of a medicament. In this sealing stopper for a syringe, a surface of the rubber body is laminated with a tetrafluoroethylene resin film or ultra-high molecular weight polyethylene film having an average roughness Ra on the central line of the surface in a range of at most 0.05 μm and a kinematic friction coefficient of at most 0.2.”
International Patent Application Publication no. 1995/030444 discloses, “A syringe comprising a barrel, a plunger and a plunger rod. The plunger can be deformed by the plunger rod to draw the radial walls of the plunger away from the inner wall of the barrel and thus reduce the friction between the plunger and the barrel, to facilitate injection. The deformation can also be used to aspirate the syringe. The invention also provides a method of delivering a liquid medium into a patient using such a syringe.”
U.S. Pat. No. 2,895,773 discloses “a piston having a piston head on which is mounted an elastic cap having one and preferably at least two rings joined by a web.
The rings are arranged to roll about shoulders formed on the piston head. The material of the piston cap may be stretched both longitudinally and radially.” and that “the principles of the invention . . . are illustrated with respect to hypodermic syringes”, but, “that the invention will function with equal effectiveness in any device in which a piston having sealing rings of elastic material can be used”.
U.S. Pat. No. 4,543,093 discloses “A plunger rod assembly for use with a syringe barrel,” comprising, “a plunger rod and a flexible thermoplastic stopper. A plunger rod includes an elongate shaft portion defining a longitudinal axis and having a tapered tip portion at the distal end thereof. The tapered tip portion includes a front portion at the distal end thereof and a circular tapered plunger rod wall connected to the front portion and having a convexly shaped surface. A flexible cup-shaped thermoplastic stopper includes an annular side wall and a continuous front wall connected to the side wall. An exterior surface of the side wall is larger in diameter than the syringe barrel inside diameter. The stopper interior includes an inside surface of the front wall and a tapered annular inside wall connected to the annular side wall and to the inside surface. The tapered annular inside wall and the inside surface define a cavity which has the tapered tip portion received therein. The tapered annular inside wall is inclined in the same direction as the tapered plunger rod wall and adjacent thereto. Cooperating structure for maintaining the positional relationship of the stopper and the plunger rod is also provided”.
Additional background art includes U.S. Pat. No. 8,038,656, US Patent Publication Application no. 2013/0060203, US Patent Publication Application no. 2007/0003584, US Patent Publication Application no. 2011/0137263, and US Patent Publication Application no. 2010/0264139. Eakins, Minn. (2009) Advances in formation, filling and inspection of prefilled syringes suitable for sensitive biopharmaceuticals. Pharmaceutical Outsourcing 10(7): 24-28. Eakins, Minn. (2010) plastic prefillable syringes and vials: Progress toward a wider acceptance. Pharmaceutical Outsourcing 11(1): 10-14. Lloyd Waxman, Harold Murray and Vinod Vilivalam, West Pharmaceutical Services, Inc., Lionville, Pa., Evaluation of piston movement and container integrity under severe storage conditions in plastic and glass prefilled syringes.